The central role of amyloid beta peptide (AP) in Alzheimer's Disease (AD) has been established by more than a decade of genetic, biochemical, animal, and human studies, but the biological functions of Ap and the role of Ap production and clearance in Ap aggregation remain very unclear. The studies proposed in this PPG bring together three Project leaders with distinct and complementary experimental approaches to these questions. These studies will address the role of synaptic activity in Ap production and clearance in mouse and cell culture models using a variety of techniques, including microdialysis and pulse-chase labeling. These studies will use a variety of tools to manipulate gene expression, including transgenic mice and lentiviral (LV) and adeno-associated virus (AAV) vectors. The viral vectors provide both temporal and spatial control of manipulation of gene expression. Viral vectors are required for experiments in the intact CNS, where DNA transfection techniques are ineffective and generation of transgenic animals requires great time and expense. The Viral Vectors Core will design and produce these vectors, a more efficient approach than generating these vectors in individual labs. The Core has provided both LV and AAV vectors to the Washington University neuroscience community for the past 6 years, with vectors provided for 43 different labs. The Core has experience with RNA silencing using shRNAs in both LV and AAV vector formats. The Core has developed new vectors to allow genetic manipulation of specific cell types. The Core will work with Project 1-3 Pis to produce both LV vectors (e.g, for orexin over expression in Project 1 and 2, for shRNA mediated knockdown of RasGRF, c-Raf, and B-Raf and orexin receptors in Project 2) and AAV vectors (for knockdown and over expression of LRPI in Project 3). The Core will use cultured neurons to test vectors to ensure the highest chance of success in more difficult and time-consuming in vivo experiments. The Core will work with Pis to devise new approaches and vectors as needed as experimental demands evolve. RELEVANCE (See instructions): Dementia ofthe Alzheimer's type (DAT) has severe consequences on quality of life and health care costs for older adults in the US. Current treatments are primarily targeted at disease symptoms and have very limited efficacy. This PPG will study how AP peptide, an important part of DAT, is made and broken down in animal models of DAT. The Viral Vectors Core will provide the tools necessary to conduct these experiments.